Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Register Calendar Latest Topics
 
 
 


Reply
  Author   Comment   Page 27 of 28     «   Prev   24   25   26   27   28   Next
LAT39

Registered:
Posts: 7
Reply with quote  #261 
A cheap and simple way to add temperature control to DC fans is to use an STC-1000 type of gadget like the one shown in this video:


I find this guys' videos to be amusing so I watched the whole thing, but the part where he gets to controlling the fans starts about 18 minutes in. He has a different goal, but it's directly applicable to what's being discussed here. One catch is that it does use AC power to run the controller, so that complicates things if one is trying to power fans directly from photovoltaic panels during a power outage.

Someone mentioned these controllers in another thread quite a while ago, so many regulars here may remember seeing them before. For the price, it's tough to beat their functionality.

stmbtwle

Avatar / Picture

Registered:
Posts: 2,731
Reply with quote  #262 
Those do appear to be nice controls, but as far as I know they don't they have any provision for controlling fan speed.
__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
dbc

Registered:
Posts: 218
Reply with quote  #263 
Thanks everybody for the suggestions.  Just as a sanity check, here's what I'm hoping to accomplish with any control modifications:

1) Keep the collector from stagnating when hot, so as to avoid any harmful out-gassing.
2) Keep the occupied space from getting uncomfortably warm on spring/fall afternoons without violating goal #1.  (During summer the collector will be covered.)

Otherwise, the collector can generate as much useful heat as possible, and most of the time that is what it will do, with the snap disc running the show.

As for any excess heat, I would actually rather capture it and store it somehow, even if it is just a tiny amount, rather than just dumping it, redirecting it, reducing fan speed, or dropping curtains, although I am willing to do any of those things to avoid another melt-down.  My sense is that the best way to store the heat is with a tight, well-insulated building, which unfortunately is not what I have.

Greg, I agree that a totally off-grid collector would be sweet - also a new topic to explore and develop.
stmbtwle

Avatar / Picture

Registered:
Posts: 2,731
Reply with quote  #264 
It's easy enough to make an off-grid collector, though whether it's worth the expense is up to you.  You'll need DC fans or pumps, and enough PV to drive them at full speed in clear weather. 

As even 12v panels can put out nearly 22v, you might be better with a 24v fan/pump. I've burned out one 12v pump running it directly on a 12v panel
A buck driver can reduce the voltage to a safe level, and can even charge your battery IF you use one.

A directly-powered fan will change speed according to the incoming energy (good) IF the panel is not too big.  An oversize panel will keep the fan running at full speed longer, and MAY require a speed control or switch.

A battery smooths things out but complicates them as well. With a battery you WILL need some kind of charge regulator and a thermostatic control of some sort.  Otherwise your fan will run all night.

But yeah you can do it.

To store heat you need MASS.  If you can't store it in the house structure the next best thing is LOTS of water.  This gets complicated but it does work.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Gordy

Registered:
Posts: 137
Reply with quote  #265 
dbc,

Did you see my door collector? I use two 7 watt PV's in series for 24 volt, a snap switch (on at 90- off at 85), and two 3.5" 24 volt fans rated at 0.1 amp. I just threw it together and got lucky, it works great. Automatic speed control by the sun ;-)

Of coarse you will need bigger everything to match your collector.

http://simplysolar.supporttopics.com/post/solar-heaters-in-frigid-temps-9608609?pid=1302771738

Gordy

__________________
Gordy,
Minnesota
Gordy

Registered:
Posts: 137
Reply with quote  #266 
dbc,

Quote:
As for any excess heat, I would actually rather capture it and store it somehow, even if it is just a tiny amount, rather than just dumping it, redirecting it, reducing fan speed, or dropping curtains, although I am willing to do any of those things to avoid another melt-down.  My sense is that the best way to store the heat is with a tight, well-insulated building, which unfortunately is not what I have.


How much room do you have for storage? here's a link that might give you an idea.



Another cabinet and jug /jar idea is like below. Line the shelve with water containers Excess hot air in at the top, cold air out at bottom. Reverse air flow when you need heat. Build to suit space available.
heat storage.jpg 



__________________
Gordy,
Minnesota
dbc

Registered:
Posts: 218
Reply with quote  #267 

Willie,  There's another way I could take the air heater off-grid:  I already have a small stand-alone, battery-based PV system - 540W of PV at 48V (4 ea. 135W / 12V nominal), Outback MPPT charge controller, 24V / 370 A-H battery (4 ea. flooded L16's), Exeltech 1100W sine wave inverter, all necessary circuit breakers.  I even have a Bogart Tri-Metric battery meter, a PV combiner box with 2 fuses (I'm only using one), and a transfer switch to switch the 'solar' receptacle between the inverter and a dedicated breaker in the utility panel. 

It's a complete working system that I could just plug the hot air collector into.  I haven't done it already for a couple reasons:
1) The present PV system load is already about what it will handle and still keep the batteries charged, and 2) the batteries are nearing end of life, to where I am already switching to utility way more than I did just a year ago (batteries are 9 1/2 years old).

I made the PV mount so I could add 4 more of the same panels.  What I could do, after I replace the batteries, is add 4 more for a second 48 V (nom.) string into the combiner box, or else add 2 more panels and re-wire the array for two 36 V strings.  36 V should still be high enough for the MPPT controller.  It's just money (gasp!).  Anyway, I decided it was better to leave the present load (couple PC's + peripherals) on the solar, because it's more vulnerable to spikes, etc.

If I did all that, I'm still at the same place regarding collector overheating protection, although powering off the PV system would save the collector if there was an extended utility outage on a sunny day.

Gordy - I want to look at your system and also the video, but right now someone's calling me.  I'll check it out though; thanks.

Bruce

Registered:
Posts: 80
Reply with quote  #268 
This has really gotten me to thinking.  I am thinking now about putting a hyro grid up on the back wall of my collector (under the back screen) of 1/2 inch risers connected to a 3/4 inch manifold with a high temp turn on temp. In case of stagnation and high temps, the drain back system would kick on and run water from a tank (or possibly the floor loop or a combination of both) to "collect" some of the overheated air to warm the water in the pipes and circulate them into the floor or a tank.  I am planning a redecoration of this room in my basement anyhow. It is next to my garage entry door and below my kitchen and I am going to tear out the current carpet flooring and replace with tile or bamboo.  I also will be removing a lot of ceiling plaster to run some new plumbing in the kitchen above to provide a hot water gravity recirculation loop. This room is cold year-around and is about 25% below grade, so the extra heat in the floor will never be too much...it likely won't even be noticeable if I install 200 sf of radiant floor heating to cool the excess from the heater.  Just a wild thought as this time, but I may develop it a little further if fund and time are available...maybe after Tax Season ;-)


dbc

Registered:
Posts: 218
Reply with quote  #269 
Gordy,
That's an interesting project.  It looks like you still have a fully-functioning door too, although I think I'd put on a pair of dark shades before walking out if the mirror was there.  But then, you said you don't use this door often.

I see you have a nice tight 'Minnesota' house, with good southern exposure, enough glazing for useful passive solar + adequate overhangs for summer shading (sure seem like there are a lot of Minnesota residents on this forum - wonder why?).  I can't believe the city wanted you to rotate the house; I think it was some Greek or Roman way back that said something like 'Only morons and barbarians build their houses so they don't face the sun'.

Bruce,
Only thing I'd be concerned about with your water/air hybrid idea is the added mass, which would have to heat up before the fan would start.  If I understand, the pipes would be empty until or unless the collector got too hot - that part makes sense to me.  I guess you could solder up the grid and set it in there loose and test with and without.  Seems like you might collect more heat this way than with an outboard air to water heat exchanger.
Gordy

Registered:
Posts: 137
Reply with quote  #270 
dbc,

Quote:
That's an interesting project.  It looks like you still have a fully-functioning door too, although I think I'd put on a pair of dark shades before walking out if the mirror was there.  But then, you said you don't use this door often.


Thanks, Some times at solar noon I open the main door and work on my tan with eye's closed of coarse [rofl]

I do want to build more and run them to the crawl space like Greg runs his to his basement. I forget what they are called, but the crawl space is made of those foam blocks with a gap that is filled with re-bar and concrete. I had to argue to get that also, $1,500 extra, over cinder block walls. It generally does not get below 50f down there, but would like warmer floors.

__________________
Gordy,
Minnesota
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics